Physicochemical characteristics and biotoxicity of water-soluble acid mine wastes from the Dabaoshan mining district

Abstract

Physicochemical analysis and bioinstrumentation have been conducted to investigate the physicochemical characteristics and biotoxicity of water-soluble acid mine wastes (AMW) in the soil layer from the Dabaoshan mining district. The results showed that the composition of the minerals could be comparatively complicated, and the minerals contain a lot of reducing sulfides and other acid matter and heavy metals. The minerals are unstable and extremely easy to dissolve in water. The pH of the solution could be as low as 2.15 with high concentrations of the heavy metals, Fe and Mn, in the solution of AMW. The concentrations of Cu, Zn, Cd, Pb, Mn and Fe in the solution were 419.5 mg/L, 0. 974mg/L, 462.8 mg/L, 0.204 mg/L, 149000 mg/L and 174.4 mg/L, respectively. The biomonitoring results showed that there was severe biotoxicity to Daphnian in the solution of AMW. A survey found no animal even in case that the pH of the solution of AMW increased from 2.15 to 7.22 by ISO-water neutralization. This indicated that the toxicity of AMW is related mainly to acid, which was also influenced significantly by the concentrations of coexisting heavy metals. It seems reasonable to suggest that the AMW from the Dabaoshan mining district could cause severe damage to the downstream aquatic ecosystem.